The present invention is directed to the field of delivery apparatus for delivering bone cement material or the like to the human or animal body.
There are certain medical procedures in which it is desirable to inject orthopaedic material into a patient.
One such known procedure is to treat a spinal column with degenerative intervertebral discs by permanently stabilising adjacent vertebrae by fusion. The disc with a pathological disorder can lead to compression of adjacent nerve roots or the spinal cord causing chronic pain to the bearer. This painful affliction is suffered by a large number of people worldwide, particularly elderly people. Intervertebral fusion can relieve the pain. The aim of intervertebral fusion is to maintain the proper intervertebral spacing and eliminate relative movement between the vertebrae, thereby treating the cause of the pain.
The spinal fusion procedure involves the replacement of the damaged, dislocated or degenerative disc with an area of fused bone. In order to encourage such bone fusion, a bone growth stimulant is used. The placement of this bone growth stimulant between the vertebrae is often carried out by insertion of an implant between the vertebrae, where the implant contains the stimulant and offers a framework for carrying the stimulant. The implant with bone growth stimulant causes bone growth in and around the implant and across the intervertebral space, thereby fusing the adjacent vertebrae into one bone mass.
Known bone growth stimulants are often granular materials. For example, autograft bone (donor bone harvested from the patient's body) or allograft bone (bone from cadavers) chippings or fragments are used, usually together with implant material such as powder/liquid material such as calcium based sulphates and phosphates.
There are other procedures in which bone graft is used in surgery, such as some forms of revision surgery.
Appropriate location of the bone growth stimulant is essential to encourage new bone growth. This placement can be difficult as the application site is often in parts of the body which are difficult to access. The use of minimally invasive procedures is preferable as it reduces trauma to the patient. Such procedures require a delivery device which can be carefully controlled by the surgeon and also which have thin delivery nozzles or ports.
Conventionally, a granular bone growth stimulant is prepared in paste form and is delivered to an application site by means of a syringe or a funnel. For example, in the case of spinal fusion, pre-loading of cages with a paste of bone growth stimulant is performed, the cages are then implanted and further paste is loaded in and around the cages. This is currently done using a tapered funnel and a spatula. The use of a tapered funnel and spatula is messy and time-consuming and does not offer the clinician sufficient control of the bone growth stimulant delivery, which is all important for a successful operation. Further, the granular material can clog in the tapered section.
Other delivery devices are known for delivering orthopaedic material. In general, these include a cylinder in which the material is held (or, in some cases, mixed). The material is then forced out of an end of the cylinder by means of, e. g., a plunger or piston into a narrower or tapered delivery nozzle for delivery to the desired site. Although such systems are useful for fluid or less viscous materials, they have not proved suitable for delivering thick pastes or highly viscous materials or for delivering materials containing relatively large chips or granules such as the bone graft materials described above. In the latter case, the transition to a narrower or tapered outlet can result in the granules separating from the paste, thereby delivering a composition, which is, at best, diluted of the granular bone growth stimulant. It may also be that the flow of the paste for delivery is prevented entirely or to an unacceptably high degree.
The present invention aims to overcome the disadvantages of known delivery apparatus for delivering thicker and/or granular materials.